Leaf-inspired Rain-energy Harvesting

The demand for renewable energy sources is steadily increasing, and one less explored method is to use the power of raindrops. As raindrops fall at high speeds and impact surfaces, they create torque on soft cantilever beams like leaves. Taking inspiration from this, we study the oscillations of piezoelectric cantilever beams caused by the impact of raindrops and propose an energy harvesting device designed to convert the bending energy into electrical energy. To evaluate the vibration and voltage response, we release a single water droplet onto the tip of the piezoelectric cantilever beam. The results show a consistent oscillation trend of frequency and damping ratio in both beam vibration and voltage. Furthermore, a single droplet experiment reveals that the beam length at 4.5 cm resulted in the highest power output. Additionally, we assessed the power generated by the device under real rainy conditions. The field test results indicate a power-law relationship between power output and beam length relative to precipitation. This research holds the potential for power generation using rainfall and could also be applied to harvest energy from water droplets in everyday activities like showers and gardening.